Voltage Control of Magnetism above Room Temperature in Epitaxial SrCo_1-xFe_xO_3-δ

Searching for new materials and phenomena to enable voltage control of magnetism and magnetic properties holds compelling interest for the development of low-power nonvolatile memory devices. In particular, reversible and nonvolatile ON/OFF controls of magnetism above room temperature are highly desirable yet still elusive. Here, we report on a nonvolatile voltage control of magnetism in epitaxial SrCo_1-xFexO_3-δ (SCFO). The substitution of Co with Fe significantly changes the magnetic properties of SCFO. In particular, for the Co/Fe ratio of ∼1:1, a switch between nonmagnetic (OFF) and ferromagnetic (ON) states with a Curie temperature above room temperature is accomplished by ionic liquid gating at ambient conditions with voltages as low as ±2 V, even for films with thickness up to 150 nm. Tuning the oxygen stoichiometry via the polarity and duration of gating enables reversible and continuous control of the magnetization between 0 and 100 emu/cm³ (0.61 μ_B/f.u.) at room temperature. In addition, SCFO was successfully incorporated into self-assembled two-phase vertically aligned nanocomposites, in which the reversible voltage control of magnetism above room temperature is also attained. The notable structural response of SCFO to ionic liquid gating allows large strain couplings between the two oxides in these nanocomposites, with potential for voltage-controlled and strain-mediated functionality based on couplings between structure, composition, and physical properties.